It's really common in China where OpenAI and Anthropic models are firewalled. There was a joke that Chinese people didn't realize how cheap DeepSeek was, because they already were using resold ChatGPT/Opus tokens at that price.

Here is a more detailed article about how it works:

https://www.chinatalk.media/p/how-to-buy-cheap-claude-tokens...

Oh that's interesting, looks like those proxies are probably also selling the data to Chinese AI companies for training.